1. Field of the Invention
The present invention generally relates to electronic equipments and, more particularly, to an electronic equipment having a heat exchanger for cooling internal parts and a rack apparatus in which such an electronic equipment is accommodated.
2. Description of the Related Art
In recent years, it is common to arrange many electric equipments in a rack having many stages so as to constitute a server or the like and install the rack in a room having air-conditioner (hereinafter, referred to as an air-conditioned room). A relatively high-temperature air generated when cooling internal parts of electronic equipments is exhausted from the housing of the electronic equipment. Many electronic equipments are accommodated in the rack, and if a plurality of such racks are installed in an air-conditioned room, a large amount of high-temperature air is discharged from the racks into the air-conditioned room. The temperature of the air-conditioned room in which the racks are installed is maintained constant at a normal temperature such as, for example, 20° C.
FIG. 1 is an illustration showing circulation of air around racks by air-conditioners. Normally, an air-conditioned room, in which racks 2 are installed, is provided with openings in a floor 4 and a ceiling so that cool air is supplied from floor openings 4a into the air-conditioned room and warm air is taken from openings of the ceiling (not shown in the figure) and suctioned into air-conditioners 6. The warm air discharged from the racks 3 is cooled by the air-conditioners 6, and, then, supplied into the air-conditioned room through the openings 4a of the floor 4. Normally, many openings 4a are provided around the racks 2 generating a large amount of heat so as to provide a well-balanced air conditioning in the air-conditioned room.
However, if many racks 2 are installed in a limited part of the area of the air-conditioned room, there may be a case where a temperature around the racks 2 becomes higher than a temperature of other areas in the air-conditioned room, which generates a heat spot where a temperature is raised locally. Additionally, if an amount of heat discharged from the racks 2 exceeds a capacity of the air-conditioners 6, it is difficult to maintain the temperature of the entire air-conditioned room constant.
Thus, there is suggested a cooling system in which a liquid-cooling type heat exchanger is provided in a rack and an internal part of each electronic equipment is liquid-cooled so as to achieve heat exchange with a cooling medium from each electronic equipment by a heat exchanger in the rack (for example, refer to Patent Document 1). In this cooling system, although heat generated by each electronic equipment is absorbed temporarily by the cooling medium, the absorbed heat is released to air in the rack and discharged to outside the rack. Thus, finally, the heat from the electronic equipments is discharged from rack to the air-conditioned room.
Moreover, there is suggested a technique to circulate air inside an electronic apparatus while cooling by providing a refrigerating machine and a heat exchanger of a cooling side in the electronic apparatus and arranging a heat exchanger of a radiation side outside the electronic apparatus (for example, refer to Patent Document 2). In this case, if the heat exchanger of the radiation side is in the air-conditioned room, whole heat from the electronic apparatus is discharged into the air-conditioned room.
Moreover, there is suggested an induction equipment in which a nonflammable insulating liquid filled in an insulated container is forcibly circulated through a heat exchanger by providing the heat exchanger in a dead space inside a tank and locating a liquid delivery pump outside the tank, and the heat exchange by the heat exchanger is achieved by causing a cooling medium to flow through an external cooling medium pipe from outside the tank so as to cool an iron core inside (for example, refer to Patent Document 3). In this case, since the cooling medium circulating in the induction equipment as an electronic apparatus is cooled by the cooling medium circulating outside the induction equipment, heat in the induction equipment can be taken out of the induction equipment, but if the radiation of heat from the cooling medium circulating outside the induction equipment is in an air-conditioned room, whole heat from the electronic apparatus is radiated into the air-conditioned room.
Moreover, there is suggested a CPU heat-radiation apparatus for cooling a CUP by providing a liquid-cooling type cooling unit to a CPU inside an electronic apparatus and circulating a cooling medium between the liquid-cooling type cooling unit and an air-cooling type cooling unit (for example, refer to Patent Document 4). In this CPU heat-radiation apparatus, the cooling medium circulates in the electronic apparatus, and the whole heat generated from the CPU is finally radiated into an air-conditioned room.
Thus, in order to cool a comparatively high-temperature air discharged from the rack 2, there is a suggestion to provide a water-cooling type heat exchanger in the rack 2 so as to discharge air of which temperature is decreased to a certain level from the rack 2. FIG. 2 is an illustration of the rack 2 provided with a water-cooling type heat exchanger 8. A plurality of electronic equipments 10 are accommodated in the rack 2. High-temperature air exhausted from the electronic equipments 10 is cooled by the water-cooling type heat exchanger 8 and turned to a low-temperature air and exhausted to outside the rack 2. A cooling-water is supplied to the water-cooling type heat exchanger 8 from outside through a cooling-water pipe 12A. The supplied cooling-water absorbs heat from the high-temperature air from the electronic equipments 10, and is discharged to outside through a cooling-water pipe 12B. Although not shown in the figure, the high-temperature cooling water discharged by the cooling-water pipe 12B is cooled by a cooling machine provided outside the air-conditioned room where the rack 2 is installed, and turned into a low-temperature cooling water and is supplied again to the cooling-water pipe 12A.
As mentioned above, by providing the water-cooling type heat exchanger 8, the temperature of the air exhausted from the rack 2 can be decreased. The heat absorbed from the air exhausted from the rack 2 is transported by the cooling-water, and radiated outside the air-conditioned room. Accordingly, the heat absorbed by the heat exchanger 8 is not radiated into the air-conditioned room, thereby reducing a load of the air-conditioning machine for air-conditioning the air-conditioned room. Additionally, by providing the heat exchanger 8 to the rack generating especially a large amount of heat, a heat spot is prevented from being generated in the air-conditioned room.
Patent Document 1: Japanese Laid-Open Patent Application No. 2004-363308
Patent Document 2: Japanese Laid-Open Patent Application No. 8-63261
Patent Document 3: Japanese Laid-Open Utility Model Application No. 6-34220
Patent Document 4: Japanese Utility Model Registration No. 3068892
As mentioned above, if the water-cooling type heat exchanger 8 is provided to the rack 2, heat exchange from a solid (heat-generating parts) to a gas (air) is performed inside the electronic equipment 10. When the air absorbed heat is exhausted from the electronic equipment 10, heat exchange from a gas (air) to a solid (fins of the heat exchanger) is performed in the water-cooling type heat exchanger 8 in the rack 2 and the air from the electronic equipment 10 is cooled and exhausted to outside the rack 2.
Generally, an efficient of heat transfer between solid and gas is lower than an efficient of heat transfer between solid and liquid. Considering an area needed to transfer the same amount of heat in an example of air and water, air requires an area ten to hundred times an area of water. In the example shown in FIG. 2, the heat generated in the electronic equipment 10 is exhausted to outside the air-conditioned room by performing the low-efficient solid-gas heat transfer two times. Accordingly, it is desirous to develop a technique which can efficiently discharge heat from an electronic equipment to outside an air-conditioned room.